YouMail (News - Alert), a provider of cloud-based communications apps and services for smartphones, announced it has reached key milestone of 2 million registered users in the United States.

This achievement follows just weeks after the company announced that it has answered more than 1 billion phone calls for users, including 500 million since September 2010.

The fact that these 2 million users have generated over 1 billion calls shows how much call activity is going through their service, according to company officials.

"What really makes this milestone special is how much of our growth is organic and how active our users are," said YouMail CEO Alex Quilici (News - Alert), in a statement. "The increasing user base is primarily from satisfied YouMail users bringing on their friends, as well as users exposing others to YouMail by sharing voicemails or using personalized greetings.”

YouMail, whose service is currently only available in the United States, has steadily grown its user base since launching its initial Visual Voicemail Plus smartphone application in 2009.

The YouMail platform supports applications for smartphones such as iPhone (News - Alert), BlackBerry and Google Android devices. It also supports third-party applications developed for other mobile operating systems, such as Windows Phone (News - Alert) 7, Windows Phone 6.5 and WebOS, as well as for the iPhone and Android platforms.

Recently the company announced the latest update to its Android (News - Alert) Visual Voicemail Plus application. The latest version of the YouMail app for Android joins recent upgrades to both BlackBerry and iPhone in significantly extending YouMail's Android user experience to make it both more fun and more useful.

YouMail achieved another significant milestone recently by receiving new funding that brings its overall total of equity and debt financing since 2007 to $12.5 million. Venture partners that participated the funding include VantagePoint Capital Partners, Siemer Ventures and the Tech Coast Angels.

The funding will be utilized to roll out a network of mobile applications and services, expand the platform and accelerate growth of Visual Voicemail Plus, its flagship service, company officials said.